Voicemail systems are widely used in telecommunications systems, such as cellular communication systems. When a calling subscriber (the A-party) places a call to a called subscriber (the B-party) and the B-party does not answer, is busy or is not reachable, the call is forwarded to the voicemail system of the relevant communications network. Many voicemail systems used by mobile network operators will then send a Short Message System (SMS) to the B-party, informing the subscriber about the missed call, and thus allowing him to place a return call.
Mobile networks typically have a limited geographical extent, and therefore, in order to allow maximum accessibility, mobile network operators typically have roaming agreements with other mobile network operators, whose networks cover other geographical areas. This allows a call to be placed to a called subscriber, even when he is outside the geographical coverage area of his home network. However, when the B-party is roaming, and misses a call, the process of forwarding the call to the voicemail system in the user's home network, as described above, may be somewhat expensive.
One known alternative solution is the Local Voicemail Deposit (LVD) solution, described briefly in the document “IN and NGIN applications portfolio” from Ericsson. With this solution, when the B-party is roaming and misses a call, the call will be forwarded locally to the voicemail. The advantage of this solution is that the local call forwarding is free of charge. However, this solution only works in a straightforward manner for postpaid subscribers. The solution for prepaid subscribers is very complex, and the result is that many operators do not use LVD for prepaid subscribers.
Instead, operators may simply disable call forwarding in the case when the B-party is roaming. That is, calls are not forwarded to voicemail, and no SMS messages notifying the B-party of the missed call are sent. This makes the system less convenient for users, and also results in a loss of revenue for the network operator because the roaming subscriber will not make the return call in response to the SMS message notifying him of the missed call.